The present invention relates to a flotation system for an offshore power generation platform. More particularly, the present invention relates to a system of maintaining the structure and buoyancy of a buoyant body used in an offshore power generation platform upon wind power or solar power generation at an offshore location at sea.
In recent years, there have been increasing instances where an offshore structure using a buoyant body has been installed at sea.
Such floating structures are used in offshore plants, container terminals, petroleum stockpiling facilities, offshore parks, or the like, and the scale thereof is also increasing.
A floating structure is generally made of concrete and is a hollow rectangular parallelepiped-shaped structure. For structural efficiency of the floating structure, partition walls are generally mounted at regular intervals in an inner space thereof to define multiple hollow portions, and these hollow portions serve to create buoyancy of a buoyant body.
In the case of a typical concrete buoyant body, when cracks occur, seawater penetrates into the buoyant body due to water pressure, leading to a reduction in buoyancy. This can lead to a problem that the buoyant body may fail to serve as a stable buoyant body.
In an effort to solve such a problem, a buoyancy maintaining method of floating a concrete structure as disclosed in Patent Document 1 (Korean Patent No. 10-0939821, issued on Feb. 2, 2010) includes an air bag mounted with a bag portion provided inside a hollow portion of the floating concrete structure and with an air inlet tube extending from the bag portion outwardly of the hollow portion for injecting air into the bag portion, wherein the air is injected into the air bag such that air pressure greater than at least draft pressure is introduced into the bag portion, and the bag portion is made larger in size than at least the hollow portion made in a standard size whereby the bag portion is brought into close contact with the inner surface of the hollow portion due to the air pressure introduced into the bag portion.
Furthermore, a floating wind turbine platform as disclosed in Patent Document 2 (PCT Publication No. WO 2009/131826, published Oct. 29, 2009) regarding as a system for a floating offshore wind power generation includes: a) at least three stabilizing columns, each column having an upper and a lower end, and an internal volume for containing a ballast fluid; b) a tower having an upper end and a lower end that is coupled to the floating wind turbine platform; c) a turbine rotor coupled to an electrical generator, the turbine rotor and the electrical generator are mounted proximate to the upper end of the tower; d) main beams interconnected to the at least three stabilizing columns; e) water-entrapment plates, each of the plates attached to the lower end of one of the stabilizing columns; and f) a ballast control system for moving the ballast fluid between the internal volumes of the at least three stabilizing columns to adjust a vertical alignment of the tower.
However, an outer wall of a buoyant body of Patent Document 1 is composed of a considerably thick concrete wall and thus is difficult to be transported to an offshore location. Furthermore, when cracks occur in the concrete wall, compressed air is supplemented into the air bag to prevent seawater from penetrating into the buoyant body. However, this may not effectively cope with a situation where the equilibrium between multiple buoyant bodies floating on the sea surface is upset due to continuous wind or storms. Additionally, Patent Document 1 has a structure in which air pressure corresponding to the draft pressure is injected, leading to a problem that the buoyant body is required to be extremely large in scale to stably float a large and heavy structure.
Meanwhile, in Patent Document 2, as a method for maintaining equilibrium between multiple buoyant bodies (columns) when the equilibrium therebetween is upset due to continuous wind, the ballast fluid is used to flow between each of the stabilizing columns, thus maintaining the equilibrium between the buoyant bodies.
However, the method for maintaining equilibrium in Patent Document 2 is problematic in that since the flow of the ballast fluid is achieved through control of the flow rate of the ballast fluid by using a pump mounted in each of the stabilizing columns, the pump is required to have a very large capacity and thus is large in size, heavy in weight, and slows in responsiveness, leading to a reduction in efficiency.